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BUREAU OF MINES / 

INFORMATION CIRCULAR/1988 







Gallium and Gallium Arsenide: 
Supply, Technology, and Uses 

By Deborah A. Kramer 



UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9208 



Gallium and Gallium Arsenide: 
Supply, Technology, and Uses 

By Deborah A. Kramer 



UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
T S Ary, Director 



Mr 



Library of Congress Cataloging in Publication Data: 



Kramer, Deborah A. 

Gallium and gallium arsenide. 












(Information circular / United 
of Mines; 9208) 


States 


Department 


of the 


Interior, 


Bureau 


Bibliography: p. 25. 












Supt. of Docs, no.: I 28.27:9208. 












1. Gallium industry. 2. Gallium 
of Mines. II. Title. 


arsenide industry. 


I. United States. 


Bureau 


TN295.U4 [HD9539] 


622 


s [338.476610675] 


88-600326 



CONTENTS 

Page 

Abstract 1 

Introduction 2 

Uses 2 

Optoelectronic devices 2 

Integrated circuits 3 

Analog ICs 3 

Digital ICs 3 

Other applications 4 

Properties and grades 4 

Resources 5 

Recovery technology 9 

Gallium recovery from bauxite 9 

Gallium recovery from zinc ore 10 

Gallium recovery from other sources 10 

Gallium purification 11 

Gallium arsenide fabrication 11 

Secondary recovery 15 

World supply and demand 16 

Production 16 

Trade 16 

Domestic demand 16 

Structure of the industry 18 

Gallium recovery, recycle, and purification 18 

Australia 18 

Canada 18 

China 18 

Czechoslovakia 18 

France 19 

Federal Republic of Germany 19 

Hungary 20 

India 20 

Japan 20 

Norway 20 

Spain 20 

Switzerland 20 

U.S.S.R 20 

United Kingdom 20 

United States 21 

High-purity arsenic production 21 

Gallium arsenide ingot, wafer, and device manufacturers 21 

Research and development 23 

Legislation and Government programs 24 

Strategic factors 24 

References 25 



ILLUSTRATIONS 

Page 

1. Beja process for recovering crude gallium from Bayer liquors 9 

2. de la Breteque process for recovering crude gallium from Bayer liquors 10 

3. Gallium recovery from zinc ore 10 

4. Gallium recovery from Musto Explorations Ltd.'s mine near St. George, UT 11 

5. Elkem A/S process for recovering gallium from aluminum smelter flue dust 12 

6. GaAs ingot growing in LEC furnace 13 

7. LEC-grown GaAs ingot and wafers 13 

8. GaAs wafer with devices 14 

TABLES 

1. Gallium reserves and reserve base 6 

2. World alumina plant capacities and gallium potential, yearend 1987 7 

3. World primary gallium production 16 

4. World secondary gallium production 17 

5. U.S. gallium imports for consumption, by country 17 

6. Japanese gallium imports, by country 17 

7. Gallium supply-demand relationships, 1977-87 18 

8. Yearend gallium plant capacities 19 

9. Gallium arsenide ingot, wafer, and device manufacturers 21 

10. U.S. import duties for gallium, January 1, 1989 24 



UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 


°C 


degree Celsius 


mt 


metric ton 


GHz 
in 


gigahertz 
inch 


run 
pet 


nanometer (one billionth 

of a meter) 
percent 


in 2 


square inch 


ppba 


part per billion atomic 


kg 


kilogram 


ppm 


part per million 


kg/yr 


kilogram per year 







GALLIUM AND GALLIUM ARSENIDE: 
SUPPLYJECHNOLOGY, AND USES 



By Deborah A. Kramer 1 



ABSTRACT 

As part of the Nation's growing concern with the competitiveness of U.S. firms in the world economy, 
especially with respect to advanced materials, the Bureau of Mines assessed the actual and potential 
recovery and manufacturing capabilities for gallium and gallium arsenide (GaAs). GaAs has advanced 
from a laboratory curiosity to a material with important "high-tech" applications within only the last few 
years, and although protected North American gallium supplies are currently considered adequate, 
consumption could grow to the point that this assessment would need reevaluation. 



'Physical scientist, Division of Mineral Commodities, Bureau of Mines, Washington, DC. 



INTRODUCTION 



Gallium-based components can be found in a variety of 
products ranging from compact disk players to advanced 
military electronic warfare systems. Compared with 
silicon, a material GaAs has replaced in some of these 
applications, components made of GaAs can emit light, 
have greater resistance to radiation, and operate at a faster 
speed and higher temperatures. But GaAs components 
are more costly and more difficult to fabricate than those 
of silicon, so they are used only in applications where the 
advantage of their properties significantly outweighs then- 
cost disadvantage. 

Gallium occurs in very low concentrations in the Earth's 
crust, and virtually all primary gallium is recovered as a 



byproduct, principally from processing bauxite to alumina. 
Most of gallium's applications require very high purity 
levels, and the metal must be refined before use until it 
contains no more than 1 ppm of total impurities. Most 
gallium metal recovery and refining facilities are in 
Europe. Through complex processing techniques, GaAs 
single crystals are produced, and optoelectronic devices 
and integrated circuits (ICs) are fabricated. Japan and the 
United States lead the world in GaAs crystal and device 
fabrication. Considerable investments are being made to 
increase processing efficiency, develop new devices, and 
increase the applications of current GaAs-based 
components. 



USES 



Gallium has limited commercial applications in its 
metallic form. Its principal use is in the manufacture of 
semiconducting compounds, mainly GaAs and gallium 
phosphide (GaP). Over 90 pet of the gallium consumed in 
the United States is used for optoelectronic devices and 
ICs. Optoelectronic devices-light-emitting diodes (LEDs), 
laser diodes, photodiodes, and solar (photovoltaic) 
cells-take advantage of GaAs's ability to convert electrical 
energy to optical energy and the reverse. The principal 
market for optoelectronic devices is in nonmilitary 
applications, including communications systems and 
consumer electronic goods. GaAs-based integrated circuits 
are used primarily in defense applications, although 
developments in recent years have increased their use in 
the commercial sector. GaAs-based integrated circuits are 
important, particularly in defense applications, because 
they can send information about five times faster, can 
withstand more radiation, and can operate at higher 
temperatures than comparable silicon-based integrated 
circuits. 

OPTOELECTRONIC DEVICES 

An LED is a semiconductor that emits light when an 
electric current is passed through it. LEDs have been in 
commercial use for many years. The first commercial 
applications for LED technology were in displays for hand- 
held calculators and digital watches. Today, LEDs are 
used in visual displays in automobiles, calculators, 
appliances, consumer electronic equipment, and a wide 
variety of industrial equipment. LEDs are also used as a 
light source in short-distance fiber optic communications 
systems. 

LEDs consist of layers of an epitaxially grown material 
on a substrate. These epitaxial layers are normally gallium 
aluminum arsenide (GaAlAs), gallium arsenide phosphide 
(GaAsP), or indium gallium arsenide phosphide 
(InGaAsP); the substrate material is cither GaAs or GaP. 
The materials used to fabricate LEDs determine the color 



of light that is emitted. With GaP substrates, the 
wavelength of light can cover the spectrum from 555 nm, 
pure green, to about 700 nm, red. With GaAs substrates, 
light emitted from an LED is limited to wavelengths at the 
red and infrared end of the spectrum. 

Laser diodes operate on the same principle as LEDs, 
but they convert electrical energy to a coherent light 
output. Laser diodes, also called semiconductor lasers or 
injection laser diodes, principally consist of an epitaxial 
layer of GaAs, GaAlAs, or InGaAsP on a GaAs substrate. 
The two most commonly used laser diodes are GaAlAs 
and InGaAsP diodes. GaAlAs laser diodes operate at 
about 780 to 900 nm and are used in a wide variety of 
consumer products and in communications systems. 
GaAlAs diodes are used in compact disk players, 
nonimpact laser printers, and optical video disk players. 
They are also used in short-range fiber optic 
communications systems, satellite communications, radar 
transmission, and local cable transmission systems. 
InGaAsP laser diodes operate at longer wavelengths, 1,300 
to 1,500 nm, and are primarily used for transmission of 
high-frequency, long-distance signals in fiber optic 
communication systems and in cable television supertrunks. 

Photodiodes, or detectors, are used to detect a light 
impulse generated by a source, such as an LED or laser 
diode, and convert it to an electrical impulse. Photodiodes 
are fabricated from the same materials as LEDs and are 
used primarily as light detectors in fiber optics systems. 
There are two types of gallium-based 
photodiodes— GaAlAs epitaxially grown on a GaAs 
substrate, used to detect light at short wavelengths, and 
InGaAsP on an indium phosphide (InP) substrate, used to 
detect light at longer wavelengths. 

Because of its ability to convert light to electrical 
energy, GaAs is an excellent material for solar cells. 
Although solar cells are not in widespread use, they have 
been used to power communications satellites. GaAs's 
advantage in this application is its electrical conversion 
efficiency; GaAs solar cells have been demonstrated to 



convert 22 pet of the available sunlight to electricity, 
compared with about 16 pet for silicon solar cells. 
Because of their higher energy efficiency, GaAs solar cells 
can be smaller than those constructed of silicon and still 
provide the same power to the satellite. Consequently, a 
satellite can carry a greater payload when GaAs is used as 
the solar cell material. GaAs is also more resistant to 
radiation than silicon; consequently, GaAs solar cells have 
a longer life in space environments (I). 2 

One defense application of optoelectronic GaAs is in 
night vision equipment. The GaAs component converts 
infrared radiation to visible light, enabling soldiers to see 
at night. Four layers of GaAlAs are epitaxially deposited 
on a GaAs substrate. The substrate and two of the layers 
are removed, yielding a thin GaAlAs film. Fabrication of 
these devices is closely controlled to prevent defects in the 
crystal structure. Even small imperfections in the night 
vision device cannot be tolerated. 

Substitute materials are available for GaAs-based 
devices in many of the optoelectronic applications. Liquid 
crystal displays (LCDs), organic compounds that change 
their light reflection and refraction properties when a 
current is applied, are the most common substitute for 
LEDs. For example, LEDs have virtually been replaced by 
LCDs in one of their original applications-digital watches. 

The principal competition for gallium-based laser diodes 
is from InP devices; because InP devices emit light at a 
longer wavelength than GaAs devices, they are suitable for 
fiber optic communications applications. However, InP 
technology is at a earlier stage of development than GaAs 
technology; thus, InP devices are more costly. 
Germanium- or silicon-based devices are the primary 
substitutes for gallium-based photodiodes. Competing 
materials for solar cells are silicon, copper indium 
diselenide, and cadmium telluride. Although not as 
efficient in thin-film solar cells as GaAs, they are generally 
less costly. 

INTEGRATED CIRCUITS 

Although ICs currently represent a smaller share of the 
GaAs market than optoelectronic devices, they are 
considered to have potential for greater growth. Two 
types of ICs are produced commercially-analog and 
digital. Analog ICs are designed to process signals 
generated by radar and military electronic warfare systems, 
as well as those generated by satellite communications 
systems. Digital ICs essentially function as memory and 
logic elements of computers. 

Analog ICs 

Analog or microwave ICs are used principally in 
defense applications. Although silicon technology is 
preferred for signals at frequencies of 3 GHz or less, such 



Italic numbers in parentheses refer to items in the list of references 
at the end of this report. 



as those in television, radios, and computers, silicon 
operates too slowly at higher frequencies. For these 
higher frequencies, up to 30 GHz, GaAs microwave ICs 
are used. One type of GaAs IC, the monolithic microwave 
IC (MMIC), combines several discrete components on one 
chip and can perform functions that used to require bulky 
circuits consisting of vacuum tubes and waveguides. 

One application of GaAs MMICs is in phased-array 
radar systems. With the development of the GaAs MMIC, 
the size of radar components can be decreased 
significantly, with improved signal-to-noise ratio. In 
phased-array radar, the antenna elements are fixed in a 
matrix in a single plane, rather than in a rotating dish, and 
are steered electronically to allow sky-borne objects to be 
individually identified. Because GaAs MMICs are small, 
the size of the antennas can be reduced significantly, 
perhaps enough to enable phased-array radar systems to 
fit on an airplane. Current phased-array radar systems 
are too large for this application. 

Another defense application of GaAs MMICs is in 
expendable decoys designed to provide fighter aircraft with 
protection against radar-directed antiaircraft missiles. 
These decoys contain a small radar transmitter and 
receiver that, when ejected from an aircraft, begin 
transmitting the same frequency of radar energy as that 
reflected from the aircraft, although at a higher strength. 
Thus, a radar-directed missile would home in on the 
decoy, rather than the aircraft. Because of the small size 
of GaAs MMIC components in the radar, these decoys are 
only about 6 in long and 1 in in diameter. 

GaAs MMICs are also a component of solid-state, 
phased-array jammers. These jammers can be surface- 
mounted on aircraft to receive and jam radar signals. 
With GaAs MMIC technology, the need for jamming pods 
is eliminated, providing space to carry additional weapons. 

GaAs MMIC technology is still in its infancy, and many 
defense applications for MMICs are being developed. 
These military applications include space-based radar, 
missile seekers, "smart" munitions and other electronic 
warfare devices, and navigation and communications. 
GaAs MMIC applications may spread to the commercial 
sector, including direct broadcast satellite receivers and 
business communications equipment, such as cellular 
telephones. 

Digital ICs 

The first digital GaAs-based ICs were introduced into 
the U.S. market as "off-the-shelf products in 1984. 
Consequently, their use in computer systems has been 
limited. In most cases, GaAs components are used in the 
high-speed supercomputers being developed. Because of 
the high cost of GaAs as compared with silicon, GaAs 
digital ICs arc not expected to replace silicon ICs in most 
high-volume commercial applications, such as personal 
computers. The use of GaAs digital ICs will be confined 
to operations in which large quantities of data must be 
interpreted in a very short time, such as in weather 
forecasting and surveillance satellites. GaAs digital ICs 



also may be used in space-borne signal processing 
applications, such as those required for the implementation 
of Strategic Defense Initiative. 

OTHER APPLICATIONS 

Gallium is used in applications other than those in 
which its semiconductor properties are important. Gallium 
oxide is used in making some single-crystal "garnets" for 
special applications. As used in the electronics industry, 
the term "garnet" refers to compounds of mixed M 2 3 
metal oxides. Gallium gadolinium garnet (GGG) is used 
as the substrate for a bubble memory device. The single 
crystals are produced by conventional means, and an 
epitaxial layer is added that contains rare earth oxides. 
These rare earth oxides provide magnetic domains, or 
bubbles, that can be oriented to store information and 
moved, by an electric field, for information readout. 
Memory devices .can be made with silicon materials, 
bubbles, or magnetic tape or disks. These three 
technologies compete on the bases of cost and size. 
Silicon devices are low cost and small, but they require 



power to retain information; otherwise the data are volatile 
and subject to loss. Although bubbles are costher and 
disks are bulkier than comparable silicon devices, they are 
nonvolatile, which makes them attractive for certain 
applications. Although not commonly used in most 
computer applications, GGG bubble memories are suited 
to dirty environments and environments that are subject to 
wide fluctuations in temperature. Commercial applications 
for GGG bubble memories include petrochemical data 
collection and plant machine control. Gallium, scandium, 
and gadolinium oxides are being used as another, mixed- 
oxide, single-crystal garnet (GSGG). GSGG has 
demonstrated improved efficiency as a laser host with 
potential inertial fusion energy applications. 

Small quantities of metallic gallium are used for low- 
melting-point alloys, for dental alloys, and as a component 
in some magnesium, cadmium, and titanium alloys. 
Gallium is also used in high-temperature thermometers 
and as a substitute for mercury in switches, because it has 
the longest liquid range of any element. Gallium has 
additional uses in glasses and mirror coatings. 



PROPERTIES AND GRADES 



GaAs has several properties that give it advantages over 
silicon in many applications. These advantages are partic- 
ularly prominent in optoelectronic applications. When 
stimulated by an electric current, GaAs gives off either 
visible or infrared light; silicon only gives off energy in the 
form of infrared radiation or heat. This makes GaAs a 
useful material for fabricating LEDs and laser diodes, 
applications for which silicon cannot be used. Both GaAs 
and silicon can convert light to electrical energy, which 
makes them useful for photodiodes and solar cells, but 
GaAs can convert more of the available light to electrical 
energy, making it more energy efficient. 

In IC applications, GaAs's properties make it especially 
appealing in defense applications. GaAs is about 10 times 
more resistant to radiation than silicon. This is essential 
in satellite operations in space, where components are 
exposed to damaging radiation from the sun. GaAs 
circuits also can operate at higher temperatures than can 
those of silicon-generally up to 350° C for GaAs compared 
with 275° C for silicon. Therefore, the need for bulky 
cooling equipment is reduced. Also, electrons move up to 
five or six times faster through GaAs than through silicon. 
This allows for faster operation of GaAs-based circuits, 



which will be of growing importance as defense applica- 
tions become increasingly sophisticated and require split- 
second decision-making capabilities. 

All of these properties make GaAs attractive, but GaAs 
has several drawbacks that limit its use only to those 
applications where its properties are crucial. The first of 
these drawbacks is its cost. Depending on the application, 
an ordinary GaAs wafer can cost $5/in 2 to $25/in 2 -a 3-in- 
diameter, undoped, semi-insulating GaAs wafer would cost 
about $185 to $200, compared with $12 for a 6-in-diameter 
silicon wafer. 

The second drawback is that GaAs is much more 
difficult to fabricate than silicon. It is much more difficult 
to grow a single-crystal ingot from two elements than from 
one, especially when the arsenic tends to diffuse out of the 
melt at temperatures lower than that required for GaAs 
crystal growth. Consequently, GaAs wafers have more 
imperfections in the crystal structure than silicon wafers, 
which may adversely affect the electronic properties of a 
device constructed on the wafer. GaAs also has lower 
production yields than silicon. From ingot to usable 
wafers, GaAs has an effective yield of about 15 pet. GaAs 
wafers are also brittle and subject to breakage during 



device fabrication, decreasing the effective yield still 
further. 

Purity requirements for the raw materials to produce 
GaAs are stringent. For optoelectronic devices, the 
gallium and arsenic must be at least 99.9999 pet pure; for 
ICs, a purity of 99.99999 pet is required. These two purity 
levels are referred to by several names-99.9999-pct-pure 
gallium is often called 6-nines, 6N, or optoelectronic (opto) 
grade, while 99.99999-pct-pure gallium is called 7-nines, 
7N, semi-insulating (SI), or IC grade. For 7N gallium, the 
total of the impurities must be less than 100 ppba. In 
addition to the difficulty of consistently producing material 



with such high purity, it is difficult to analyze for the small 
quantity of impurities. Certain impurities can cause more 
problems during GaAs production than others. The 
impurities of most concern are calcium, carbon, copper, 
iron, magnesium, manganese, nickel, selenium, silicon, 
sulfur, tellurium, and tin. Generally these elements should 
be present in concentrations less than 1 ppba in both the 
gallium and arsenic. Lead, mercury, and zinc should be 
present in concentrations less than 5 ppba. Although 
aluminum, chlorine, and sodium are often present, each of 
their concentrations should be less than 10 ppba. 



RESOURCES 



Although gallium is as abundant in the Earth's crust as 
lead, it is widely disseminated and is rarely found in 
concentrations greater than 0.1 pet. Consequently, gallium 
is nearly always recovered as a byproduct during 
processing of ores or other materials to recover other 
metals. The principal materials in which gallium is found 
are bauxite, coal, phosphate ores, and sphalerite (zinc ore). 
Of these, gallium is currently commercially recovered 
during the processing of bauxite to alumina and the pro- 
cessing of sphalerite to zinc. 

Bauxite generally is considered the most likely source of 
byproduct gallium, because gallium occurs in virtually all 
bauxites and is somewhat concentrated during the 
extraction of alumina from bauxite via the Bayer process. 
The gallium content of bauxite varies depending on the 
individual deposit, averaging about 50 ppm for the world. 
Bauxites containing high quantities of gallium, 70 to 
80 ppm, are found in India, Suriname, and the United 
States. Table 1 shows an estimate of the world gallium 
reserves and reserve base available from bauxite, based 
on bauxite reserves and reserve base and the average 
gallium content of the bauxite in each country (2). 

Although world gallium reserves of over 1 million mt 
are available from bauxite, much of this bauxite will not be 
mined for many decades, and only about 40 pet of the 
available gallium is recoverable with current technology. 
Table 2 presents a projection of the annual gallium 
capacity of each of the world's Bayer alumina plants, based 
on each plant's alumina capacity, sources of bauxite, 
bauxite-to-alumina ratio, and gallium content. Australia, 
Jamaica, the U.S.S.R., and the United States have the 
most potential for gallium recovery from bauxite. 



Because gallium is not recovered at many alumina 
plants throughout the world, and because most of the 
gallium originally contained in the bauxite does not 
dissolve during the alumina extraction process, large 
quantities of gallium are discarded in the red mud residue. 
Although not currently considered a gallium resource 
material, the red mud residue represents a large potential 
gallium resource. Much of the residue is contained in 
tailings ponds near the alumina refineries and would be an 
easily accessible resource. 

Zinc ores also represent a significant source of gallium, 
although not all zinc ores contain gallium. Sphalerite, a 
zinc sulfide mineral, generally contains detectable 
quantities of gallium, but little quantitative information is 
available to present an accurate assessment of the gallium 
potential of these ores. Based on the assumption that the 
average gallium content of sphalerite is 50 ppm, domestic 
sphalerite reserves of 21 million mt contain 1,050 mt of 
gallium. Total world reserves of 147 million mt of 
sphalerite may contain as much as 7,350 mt of gallium. 
The countries with the largest sphalerite reserves are 
Canada, the United States, and Australia. As with bauxite, 
much of this ore will not be mined for many decades and 
represents a long-term source of gallium. 

Coal fly ash and phosphate flue dusts also contain 
gallium, but because of the availability of gallium from 
bauxite and sphalerite, it is unlikely that these materials 
would be used as principal sources of gallium, although 
technology to recover gallium from these materials has 
been developed. 



Table 1. - Gallium reserves and reserve base 1 



Country 



Bauxite 

reserves, 

icfmt 



Bauxite 

reserve base, 

IC^rnt 



Gallium 

content, 

pet 



Gallium, 

reserves,'' 

mt 



Gallium 

reserve base, 2 

mt 



Australia 

Brazil 

Cameroon 

China 

Dominican Republic 

France 

Germany, Federal Republic of .... 

Ghana 

Greece 

Guinea 

Guyana 

Haiti 

Hungary 

India 

Indonesia 

Italy 

Jamaica 

Malaysia , 

Mozambique 

Pakistan 

Romania 

Sierra Leone 

Spain 

Suriname 

Turkey 

U.S.S.R 

United States 

Venezuela 

Yugoslavia 

Zimbabwe 

Other 

Total 

NAp Not applicable. 
'Reserve base includes reserves. 
2 Based on a 40-pct gallium recovery. 
3 Rounded. 



4,440,000 

2,800,000 

680,000 

150,000 

30,000 

30,000 

2,000 

450,000 

600,000 

5,600,000 

700,000 

10,000 

300,000 

1,000,000 

750,000 

5,000 

2,000,000 

15,000 

2,000 

20,000 

50,000 

140,000 

5,000 

575,000 

25,000 

300,000 

38,000 

320,000 

350,000 

2,000 

200,000 



4,600,000 

2,900,000 

800,000 

150,000 

45,000 

40,000 

2,000 

560,000 

650,000 

5,900,000 

900,000 

14,000 

300,000 

1,200,000 

805,000 

5,000 

2,000,000 

15,000 

2,000 

20,000 

50,000 

160,000 

5,000 

600,000 

30,000 

300,000 

40,000 

350,000 

400,000 

2,000 

200,000 



21,589,000 



23,045,000 



0.006 
.005 
.004 
.006 
.004 
.003 
.003 
.003 
.003 
.003 
.005 
.004 
.003 
.007 
.004 
.003 
.006 
.003 
.003 
.003 
.003 
.004 
.003 
.008 
.003 
.005 
.007 
.003 
.003 
.003 
.003 



NAp 



106,560 

56,000 

10,880 

3,600 

480 

360 

24 

5,400 

7,200 

67,200 

14,000 

160 

3,600 

28,000 

12,000 

60 

48,000 

180 

24 

240 

600 

2,240 

60 

18,400 

300 

6,000 

1,064 

3,840 

4,200 

24 

2,400 



3 400,000 



110,400 

58,000 

12,800 

3,600 

720 

480 

24 

6,720 

7,800 

70,800 

18,000 

224 

3,600 

33,600 

12,880 

60 

48,000 

180 

24 

240 

600 

2,560 

60 

19,200 

360 

6,000 

1,120 

4,200 

4,800 

24 

2,400 



J 430,000 



Table 2. - World alumina plant capacities and gallium potential, yearend 1987 



Company name 


Plant location 


Bauxite sources 


Annual 

alumina capacity, 

lO'mt 


Annual 

gallium potential, 

mt 


Australia: 

Alcoa of Australia Ltd 

Do 

Do 

Nabalco Pty. Ltd 

Queensland Alumina Ltd 

Worsley Alumina Pty. Ltd 


Kwinana, Western Australia . . 
Pinjarra, Western Australia . . . 
Wagerup, Western Australia . . 
Gove, Northern Territory .... 

Gladstone, Queensland 

Worsley, Western Australia . . . 


Australia 

. . do 

. . do 

. . do 

. . do 

. . do 


1,400 
2,300 
570 
1,100 
2,300 
1,000 


224 
369 
116 
161 
328 
204 


Total Australia 


8,670 


1,402 




Saramenha, Minas Gerais . . . 
Pocos de Caldas, Minas Gerais 

Sao Luis, Maranhao 

Sorocabo, Sao Paulo 


Brazil 

. . do 

. . do 

. . do 




Brazil: 

Alcan Aluminio do Brazil 

Alcoa Aluminio S.A 

Aluminio do Maranhao S.A. . . . 
Cia Braziliera de Aluminio .... 


120 
180 
500 

400 


13 
19 
58 
44 


Total Brazil 


1,200 
1,225 


134 


Canada: Alcan Basic Raw Materials 


Jonquiere, Quebec 

Province of Liaoning 

Province of Guizhou 

Province of Shanxi 

Province of Shangdong 

Province of Shaanxi 

Province of Hainan 


Brazil, Guinea, 
Guyana. 

China 


73 


China: 

Fushun Alumina Plant 


250 
220 
200 
220 
130 
180 


35 


Guiyang Alumina Plant 

Hejin Alumina Plant 

Nanding Alumina Plant 

Tian Alumina Plant 

Wenchang Alumina Plant 


. . do 

. . do 

. . do 

. . do 

. . do 


30 
28 
30 
18 
25 


Total China 


1,200 
100 


166 


Czechoslovakia: 

ZNSP Kovohute Praha 


Ziar nad Hronom 


Hungary, 
Yugoslavia. 

France, Guinea . . 
. . do 


7 




Gardanne 

La Barasse 




France: 

Aluminium Pechiney 

Do 


700 
340 


62 
30 








Total France 


1,040 


92 




Stade 

Bergheim 


Australia, Guinea. 
Australia, Sierra 

Leone. 
Australia, Guinea . 
. . do 

Greece 

Guinea 




Germany, Federal Republic of: 
Aluminum Oxid Stade GmbH . . 
Martinswerk GmbH 


600 

350 

430 
120 


57 
39 


Vereinigte Aluminium Werke AG 
Do 


Lippewerke, Lunen 

Nabrewerke, Schwandorf .... 

iny 

Distommon 

Kimbo 

Linden 

Ajka 


41 
11 


Total Federal Republic of Germ; 

Greece: Aluminium de Grece S.A. . 
Guinea: Friguia Societe D'Economie 
Guyana: Guymine 


1,500 

600 
700 
354 


148 

41 
43 


Guyana 

Hungary 

. . do 

. . do 


35 






Hungary: 

Hungarian Aluminium Corp. . . . 

Do 

Do 


475 
335 
110 


34 


Alamasfuzito 

Mosonmagyarovar 


24 
8 


Total Hunqary 


920 


66 




Korba, Madhya Predesh .... 
Renukoot, Utter Pradesh .... 

Belgaun, Karnataka 

Muri, Bihar 


India 




India: 

Bharat Aluminium Co. Ltd 


200 
160 
160 
72 
60 
800 


31 


Hindustan Aluminium Corp. Ltd. 

Indian Aluminium Co 

Do 


. . do 

. . do 

. . do 

. . do 

. . do 


25 
25 

11 


Madras Aluminium Co. Ltd. . . . 
National Aluminium Co. Ltd. . . . 


Mertur, Tamil Nadu 

Damamjodi, Orissa 


9 
122 


Total India .... 


1,452 
800 


223 


Ireland: Aughinish Alumina Ltd. . . 


Aughinish, Limerick County . . 


Guinea 


48 



Table 2. • World alumina plant capacities and gallium potential, yearend 1 987— Continued 



Company name 



Plant location 



Bauxite sources 



Annual 

alumina capacity, 

lO^mt 



Annual 
lium potential, 
mt 



Italy: 

Aluminio Italia 



Porto Marghera 



Eurallumina SpA 
Total Italy . . . 



Porto Vesme, Sardinia 



Australia, 
Brazil, Guinea, 
Yugoslavia. 

Australia, Guinea. 



Jamaica: 

Alpart 

Clarendon Alumina Production 
Ltd. 

Jamaican Joint Venture 

Do 

Total Jamaica 



Spur Tree 

Halse Hall, Clarendon 

Ewarton, St. Catherine 
Kirkvine, Manchester . 



Jamaica 
.. do 

.. do 

. . do 



Japan: Nippon Light Metal Co. 



Romania: 

Alumina Enterprise 
Do 



Shimizu 



Oradea 
Tulcea . 



Australia, 
Indonesia. 



Romania 
.. do . 



Total Romania 



Spain: Aluminia Espanola S.A. 
Suriname: Paranam Refinery 

Joint Venture. 
Turkey: Etibank Alumina Plant 
U.S.S.R.: 

Bogslav Aluminium 

Dnjepr Aluminium 



San Ciprian 
Paranam . . 



Guinea . . 
Suriname 



Seydisehir 



Turkey 



Nikolaev Alumina 



Novokuzneck Alumina 
Pavlodar Alumina 
Tikhvin Alumina 



Northern Urals 
Zaporashye . . 



Black Sea, South Ukraine 



Kemerovo 

Kazakhstan, Central Asia 
Leningrad 



U.S.S.R 

U.S.S.R., Guinea, 
Yugoslavia, 
Hungary, 
Jamaica. 

Guinea, Yugosla- 
via, Jamaica, 
Brazil, Guyana. 

U.S.S.R 

. . do 

U.S.S.R., Guinea, 
Yugoslavia, 
Brazil, Jamaica. 



200 



720 



920 



1,180 
550 



500 

800 
1,352 

200 



350 
300 



1,000 



250 
500 
350 



20 



86 



106 



177 
83 



566 
558 


85 
77 


2,854 
380 


422 

44 


250 
250 


17 

17 



34 

48 
234 

14 



50 
30 



74 



35 
71 
35 



Ural Aluminium 


Urals 


U.S.S.R 


250 


35 




Total U.S.S.R 






3,000 


330 












United States: 








Aluminum Co. of America .... 


Point Comfort, TX 


Guinea, Suriname. 


1,210 


125 




Kaiser Aluminum & Chemical 


Gramercy, LA 


Jamaica 


725 


109 




Corp. 












Reynolds Metals Co 




Guinea, Brazil, Aus- 
tralia, Jamaica. 


1,256 


142 




Total United States 


3,191 


376 




Venezuela: 








Interamericana de Alumina C.A. 


Puerto Ordaz, Orinoco .... 


Guyana, Brazil, 
Suriname. 


1,300 


156 




Yugoslavia: 








Energoinvest Aluminium 


Bacevici, Mostar, Bih 


Yugoslavia 


280 


19 




Do 


Zvornick, Vlasneica 


. . do 


600 


42 




Kombinat Aluminijuma Titograd 


Titograd, Montenegro .... 


. . do 


280 


19 




Tvornica Lakih Metala 


Obravac, Dalmatia 


. . do 


300 


21 




Unial Tovarna Glinice in Alumina 


Kidricevo, Slovenia 


Yugoslavia, 
Guinea. 


140 


9 






1,600 


110 




World total 






35,858 


4,352 





RECOVERY TECHNOLOGY 



GALLIUM RECOVERY FROM BAUXITE 

Throughout the world, alumina is recovered from 
bauxite by the Bayer process. In this process, alumina is 
extracted from bauxite through digestion with a hot caustic 
solution. After the slurry is cooled and solid residue is 
separated from the aluminum -containing liquor, the 
solution is seeded with alumina trihydrate crystals to 
precipitate the dissolved aluminum as alumina trihydrate. 
Alumina trihydrate is separated from the solution and 
calcined to produce alumina, while the caustic solution is 
recycled to the bauxite digestion step. 

Because gallium is chemically similar to aluminum, it 
tends to remain with aluminum during processing. When 
the aluminum is extracted during digestion, gallium is also 
extracted. Gallium is not removed from the solution 
during subsequent processing steps, and because the 
solution is recycled, gallium builds up to an equilibrium 
concentration of 100 to 125 ppm. When gallium recovery 
is desired, a bleed stream is separated from the caustic 
solution before it is recycled to the digestion step. Crude 
gallium metal, 97.0 to 99.9 pet pure (3N), is recovered by 
two principal processes-the Beja process and the de la 
Breteque process. Simplified flowsheets for these pro- 
cesses are shown in figures 1 and 2. 

In the Beja process, carbon dioxide is injected into the 
bleed solution to precipitate aluminum not recovered in 
the Bayer process as alumina trihydrate. The trihydrate is 
separated from the solution, and the galhum-containing 
solution is carbonated again. In the second carbonation, 
a gallium precipitate, containing between 0.3 and 1 pet 
gallium, is recovered. Both of the carbonation steps are 
carefully controlled so that about 90 pet of the aluminum 
is removed during the first carbonation and 90 pet of the 
gallium is precipitated during the second carbonation. 
After the gallium precipitate is separated from the solu- 
tion, which is recycled to the Bayer process, the precipitate 
is dissolved in a caustic solution to increase the gallium- 
to-aluminum ratio. This solution is electrolyzed to recover 
crude gallium as a liquid. The spent solution is recycled 
to the Bayer process (3). 

In the de la Breteque process, a bleed stream from the 
Bayer process is concentrated by evaporation to increase 
the gallium concentration. Concentrated solution is 
directly electrolyzed using a highly agitated mercury 
cathode. The agitation allows the gallium to form an 
amalgam with the mercury. When the gallium concen- 
tration reaches about 1 pet in the amalgam, it is drawn off 
and leached with a caustic solution. This yields a 
concentrated gallium solution from which crude gallium 
can be recovered by electrolysis (4). 

Because mercury losses are significant owing to the high 
level of cathode agitation in the de la Breteque process, a 
modification to the process was developed by Vereinigte 



Bleed stream Bayer 
liquor 



1 



CARBONATION 



LIQUID-SOLID 
SEPARATION 



"►Al203-3H 2 



CARBONATION 



LIQUID-SOLID 
SEPARATION 



± Recycle liquor 
to Bayer process 



rGallium concentrate 



NaOH- 



REDISSOLVING 



ELECTROLYSIS 



Recycle liquor 
to Bayer process 



Crude gallium 

Figure 1.— Beja process for recovering crude gallium from 
Bayer liquors. 



Aluminium Werke AG (VAW) of the Federal Republic of 
Germany. Rather than preparing a gallium-mercury 
amalgam by electrolysis, a sodium-mercury amalgam is 
prepared by electrolyzing the caustic solution with a 
mercury cathode. Gallium is then extracted by a cemen- 
tation process as the gallium in solution replaces the 
sodium in the amalgam. Subsequent gallium recovery 
follows the same steps as in the de la Breteque process. 

Although the de la Breteque process and the VAW 
modification are the most commonly used processes, sev- 
eral companies have developed proprietary recovery tech- 
niques that they claim are less costly than conventional 
processes. Rhonc-Poulenc S A. uses a liquid-liquid extrac- 
tion technique at its plant in France to recover gallium 
from Bayer liquors. Sumitomo Chemical Co. Ltd. of 
Japan uses an unidentified absorbent to extract gallium 
directly from Bayer liquor. 



10 



Bleed stream Bayer 
liquor 



EVAPORATION 



Concentrated gallium solution 



ELECTROLYSIS 



Recycle 
NaOH 
solution 



w Recycle liquor 
to Bayer process 



^Gallium-mercury amalgam 
NaOH 



LEACHING 



ELECTROLYSIS 



▼ 
Crude gallium 



Figure 2.— de la Breteque process for recovering crude gallium 
from Bayer liquors. 



GALLIUM RECOVERY FROM ZINC ORE 

Dowa Mining Co., the only company that currently 
recovers gallium from zinc ore, uses an electrolytic method 
for producing zinc. In recovering zinc by this method, a 
roasted zinc concentrate is leached with sulfuric acid to 
produce a zinc sulfate solution, which is neutralized to 
remove impurities. Impurities that precipitate from the 
zinc sulfate solution include gallium, aluminum, and iron. 
Leaching this residue with a caustic solution extracts the 
gallium, along with the aluminum and iron impurities. 
After the remaining residue is separated from the gallium- 
containing solution, the solution is neutralized to precipi- 
tate the metal hydroxides. The hydroxide solids are 
leached with hydrochloric acid to dissolve gallium and 
aluminum, and the gallium is separated from the alumi- 
num in solution by solvent extraction with ether. Distilla- 
tion of the ether solution yields a gallium-rich residue that 
still contains some iron, which is removed by treating the 
residue with a strong caustic solution to extract the galli- 
um, while leaving the iron as a solid. Iron residue is 
filtered from the gallium-containing solution, and crude 
gallium is recovered by electrolysis. A simplified flowsheet 
for this process is shown in figure 3. 

GALLIUM RECOVERY FROM OTHER SOURCES 

Other sources of gallium that have been investigated 
include phosphate flue dust, coal fly ash, aluminum smelter 
flue dusts, and iron oxide minerals found in Utah. The 
only sources that have been commercially treated to 



Gallium-containing residue from 
zinc sulfate solution purification 



LEACHING 



I 



•NaOH 



NEUTRALIZATION 



LIQUID-SOLID 
SEPARATION 



£ 



-HC1 



-^Waste solution 



LEACHING 



etal hydroxides 



Recycle 
ether 



I 



HC1 



SOLVENT 
EXTRACTION 



-► Waste solution 



DISTILLATION 



I 



Gallium residue 



NaOH 
solution 



4 


REDISSOLVING 


4- 


— 


i 




LIQUID-SOLID 
SEPARATION 


k, 




w 


V 








^ 









-NaOH 



^Iron precipitate 



Crude gallium 



Figure 3.— Gallium recovery from zinc ore. 



recover gallium are the minerals in Utah and aluminum 
smelter flue dusts. In 1986, St. George Mining Corp., a 
subsidiary of Musto Explorations Ltd., began recovery of 
gallium from an abandoned copper mine near St. George, 
UT. Although much of the copper had been mined, the 
remaining iron oxide minerals contained an average of 
0.042 pet gallium. Because this source material is different 
from bauxite or zinc ore, a new processing technique was 
developed, as shown in figure 4. 

Crushed ore is leached with sulfur dioxide gas, a 
sulfuric acid solution, and fluorspar to extract gallium, 
along with germanium, copper, iron, and zinc. After the 
insoluble impurities are separated, copper is cemented by 
the addition of iron and separated from the gallium-con- 
taining solution. Dissolved germanium is precipitated as 
a sulfide by injection of hydrogen sulfide gas into the 
solution, and the precipitate is removed and treated to 
recover germanium dioxide. The solution, containing 
gallium, zinc, and iron, undergoes solvent extraction, where 
the gallium and zinc are extracted into the organic solu- 
tion; the iron remains in the aqueous phase. Gallium and 



11 



H 2 S0 4 " 
SOo' 



Ore 



LEACHING 



Iron ■ 



LIQUID-SOLID 
SEPARATION 

I 



-Fluorspar 

Residue to 
tailings pond 



> CEMENTATION 



LIQUID-SOLID 
SEPARATION 



H S' 



i 



-^Cement copper 



GERMANIUM 
PRECIPITATION 



LIQUID -SOLID 
SEPARATION 



Recycle 

organic 



Precipitate to 
'germanium recovery 



SOLVENT 
EXTRACTION 



STRIPPING 



NHi 



GALLIUM 
PRECIPITATION 



LIQUID-SOLID 
SEPARATION 



I 



Ferrous sulfate 
solution 



_^Zinc sulfate 
solution 



Gallium hydroxide 



PURIFICATION 



ELECTROLYSIS 



▼ 
Crude gallium 

Figure 4.— Gallium recovery from Musto Explorations Ltd.'s 
mine near St George, UT. 



zinc are stripped from the organic phase, and ammonia is 
injected into the stripped solution to precipitate gallium 
hydroxide. Gallium hydroxide precipitate is separated 
from the zinc solution and purified, and 99.999-pct-pure 
(5N) gallium metal is recovered by electrolysis. The elec- 
trolytic technology used at Musto's plant is proprietary 
technology licensed from Cominco Ltd. 

In July 1987 Elkem A/S of Norway began producing 
crude gallium using aluminum smelter flue dust as a 
source material. Dusts generated at two smelters in 
Mosjoen and Tyssedal are blended to yield material with 
the following average concentration: Carbon, 33 pet; fluo- 
rine, 17 pet; oxygen, 17 pet; aluminum, 13 pet; sodium, 
9 pet; iron, 6 pet; sulfur, 3 pet; calcium, 1.5 pet; and gal- 
lium, 0.5 pet. Leaching the flue dust with hydrochloric 
acid extracts the gallium. Solids are filtered from the 



liquid phase and mixed with portland cement before 
disposal. The liquid phase undergoes a series of solvent 
extraction stages to separate gallium from dissolved 
impurities. After cleaning and stripping, crude gallium is 
recovered by electrolysis of the water phase. A simplified 
flowsheet for this process is shown in figure 5. 

GALLIUM PURIFICATION 

For most applications, purity requirements for gallium 
are either 6N or 7N. Crude gallium is purified in essen- 
tially two steps-the first step produces 99.99-pct-pure (4N) 
gallium, and the second produces 6N to 7N metal. 

Many of the impurities in crude gallium occur in the 
surface oxide or as finely dispersed phases in the metal. 
Liquid gallium filtration and heating under vacuum remove 
these types of impurities. Metallic impurities can be 
reduced to less than 0.01 pet, producing 4N gallium, by 
sequential washing with hydrochloric acid. Another 
method that can be used is electrolytic refining, which 
involves anodic dissolution of gallium in an alkaline solu- 
tion, and then deposition at a liquid gallium cathode. 

The principal method used to produce 6N and 7N metal 
is gradual crystallization of molten gallium. In this pro- 
cess, impurities remain in the liquid phase and do not con- 
taminate the gallium crystal. Crystallization is repeated 
until gallium of the desired purity is obtained. Another 
method of producing high-purity gallium is to convert the 
gallium to a halide compound, such as gallium trichloride, 
which is then zone-refined. High-purity gallium is 
recovered by electrolysis of the halide compound. 

GALLIUM ARSENIDE FABRICATION 

GaAs single crystals are more difficult to fabricate than 
those of silicon. With silicon, only one material needs to 
be controlled, whereas with GaAs, a one-to-one ratio of 
gallium atoms to arsenic atoms must be maintained. At 
the same time, arsenic volatilizes at the temperatures 
needed to grow crystals. To prevent a loss of arsenic, 
which would result in the formation of an undesirable 
gallium-rich crystal, GaAs ingots are grown in an enclosed 
environment to contain the arsenic. 

Two basic methods are used to fabricate GaAs single- 
crystal ingots-the boat-growth, horizontal Bridgeman (HB) 
or gradient freeze technique, and the liquid-encapsulated 
Czochralski (LEC) technique. Ingots produced by the HB 
method are D-shaped and have a typical cross-sectional 
area of about 2 in 2 . By contrast, single-crystal ingots 
grown by the LEC method are round and are generally 
3 in in diameter, with a cross-sectional area of about 7 in . 

In HB growth, gallium and arsenic in the proper ratio 
are placed in one end of a silicon dioxide (quartz) or 
pyrolytic boron nitride boat. A seed GaAs crystal is 
contained at the other end of the boat. The boat is placed 
in a sealed quartz tube, which is evacuated to a very low 
pressure. The tube is placed in a multiple-zone furnace, 
where the gallium and arsenic react to form GaAs. The 



12 





A 


.umlnum smelter flue 


dust 






LEACHING 






HC1 






1 








LIQDID-SOLID 
SEPARATION 




^ r> : J 












1 








4 


SOLVENT 
EXTRACTION 






Recycle 
organic 


1 


f 








STRIPPING 








^ 








1 


r 








ELECTROLYSIS 




^ « *i 












v 1 
Crude 


r 

gallium 







Figure 5.— Elkem A/S process for recovering gallium from 
aluminum smelter flue dust 



compound is heated to 1,240° C, the melting point of 
GaAs. The GaAs melt is slowly cooled from the seed end, 
resulting in single-crystal growth. In the LEC method of 
crystal growth (fig. 6), carefully weighed pieces of gallium 
and arsenic are melted in a pressurized vessel (crystal 
puller). The GaAs melt is contained in a crucible con- 
structed of either high-purity quartz or pyrolytic boron 
nitride. The melt is covered with a layer of boric oxide, 
which retards arsenic loss from the melt by sublimation. 
A seed crystal is lowered through the boric oxide into the 
melt and slowly withdrawn as both the seed and crucible 
are rotating. 

Each of these methods produces GaAs ingots with par- 
ticular advantages and disadvantages. Crystals formed by 
the boat-growth method are particularly suitable for opto- 
electronic applications because their structure is highly 
perfect with respect to dislocations. Optoelectronic devices 
also require crystals with a high doping concentration, 
which boat-grown crystals readily provide, because the 
silicon dissolved from the quartz boat contributes to crystal 
doping. This latter benefit becomes a problem if semi- 
insulating GaAs crystals for ICs are being produced. The 
silicon impurities are called shallow donors, or N-type 
dopants. To compensate for these impurities, either a 
controlled quantity of gallium oxide can be added to the 
melt, or chromium, a deep acceptor or P-type dopant, can 
be added. Crystal growth also can be accomplished in a 
boron nitride container, which eliminates any contact with 
silicon-containing material during growth. The shape of 
the HB-grown ingot makes it inconvenient for subsequent 
wafer processing, because automated wafer processing sys- 
tems are designed to handle round wafers. LEC-grown 
ingots generally contain more crystal structure defects, i.e., 
they have higher dislocation densities, than HB-grown 



ingots. This affects the electronic properties of the device 
constructed on the GaAs. Dislocation densities in HB 
wafers normally run between 500 and 20,000 per square 
centimeter; those in LEC wafers can be as large as 100,000 
per square centimeter. Because chips are batch processed, 
wafer by wafer, the larger the wafer, the more chips per 
wafer, and the lower the cost per chip. A 3-in-diameter 
LEC-grown wafer can yield more of the same-size chips 
than a 2- by 1.5-in HB wafer. Conversely, the capital costs 
for an HB system are significantly less than those for an 
LEC system. 

After the ingots are grown, the ends are cut off, and the 
ingots are shaped by grinding the edges. Ingots are then 
sliced into wafers (fig. 7). Wafers go through several 
stages of surface preparation, polishing, and testing before 
they are ready for device manufacture or epitaxial growth. 
Wafer preparation steps are done in a clean room and 
with minimal contact to avoid introducing surface contami- 
nants. In LEC growth, the effective yield from starting 
material to finished wafers is currently less than 15 pet. 

Pure GaAs is semi-insulating, which means that it is not 
a conductor of electricity. In order for GaAs to conduct 
electricity, a small number of atoms of another element 
must be incorporated into the GaAs crystal structure. This 
is called doping. These atoms act as electron donors or 
electron acceptors. Electron donor atoms have one more 
electron than the atoms that they are replacing, and this 
electron is free to move within the crystal as an electrical 
charge carrier. Electron acceptors have one less electron 
than the atoms they are replacing and behave as positively 
charged particles to serve as electrical charge carriers (5). 

To manufacture devices from GaAs wafers, the wafers 
must be doped with another metal or metals. Normally, 
this is accomplished either by ion implantation or by some 
type of epitaxial growth. Because GaAs is a semi- 
insulating substrate, no special isolation areas are required 
to separate each device fabricated on the chip. This 
results in more compact, higher density circuits, which add 
to GaAs's speed advantage. 

In ion implantation, ions of another metal are 
implanted into specific areas of the semi-insulating GaAs 
to make those areas electronically active. Areas of the 
chip that are to remain semi-insulating are covered with a 
photoresist mask before ion implantation. The process of 
ion implantation may be repeated several times with dif- 
ferent metals on different areas of the chip, depending on 
the type and complexity of the device being manufactured. 
After ion implantation, the GaAs must be annealed at 
about 850° C in order to activate the implanted dopants 
and remove crystal damage incurred during implantation. 
When annealing, as in crystal growth, several techniques, 
including encapsulation of the chip, are used to prevent 
arsenic losses at the elevated temperature. After doping, 
optoelectronic device or IC manufacture can be completed 
through deposition of layers of metals and insulators by 
various techniques. 

A similar technique, called ion cluster beam, is not as 
frequently used as ion implantation. In this technique, ions 
are grouped together and implanted into the wafer at 



13 




Figure 6.-GaAs Ingot growing in LEC furnace (Courtesy Morgan Semiconductor Div. of Ethyl Corp.) 




Figure 7.-LEC-grown GaAs Ingot and wafers (Courtesy Morgan Semiconductor Div. of Ethyl Corp.) 



14 



lower speeds than used in ion implantation. This process 
is reported to result in less damage to the crystal structure. 

The deposition of an epitaxial layer is another means of 
creating electronically active regions on the GaAs 
substrate. There are four principal methods for growing 
epitaxial layers-liquid-phase epitaxy (LPE), vapor-phase 
epitaxy (VPE), metal-organic chemical vapor deposition 
(MOCVD), and molecular beam epitaxy (MBE). LPE is 
an earlier method of epitaxy that is generally not 
considered suitable for complex semiconductor production 
because it cannot be as precisely controlled as the other 
three techniques. In LPE, the substrate wafer is contained 
in a graphite boat within a quartz furnace tube, where it is 
contacted with solutions containing the metals to be 
deposited. Cooling the solution causes the metals to 
precipitate on the substrate. LPE produces relatively thick 
epitaxial layers, and the boundaries between layers are 
gradual rather than sharply defined. 

Two methods of VPE are used to grow epitaxial layers 
on a GaAs substrate-the hydride method and the chloride 
method. In VPE, GaAs substrates are mounted in a 
reactor. To make GaAsP epitaxial layers, two gaseous 
streams are introduced into the reactor. In the hydride 
process, one gas stream combines arsine (AsH 3 ) and 
phosphine (PH 3 ) with a hydrogen carrier gas; the other gas 
stream is a hydrochloric acid gas that has been passed over 
a gallium reservoir to form gallium trichloride, and that 
also is mixed with a hydrogen carrier gas. Dopants are 
added to the gas streams if necessary. Gallium trichloride 
reacts with the AsH 3 and PH 3 gases to deposit a GaAsP 
layer on the substrate. In the chloride process, arsenic 
trichloride and phosphorus trichloride gases are substituted 
for AsH 3 and PH 3 . VPE technology can coat multiple 
wafers at the same time, and the layer thickness, molecular 
composition, and dopant concentration can be more closely 
controlled than with LPE. 

In MOCVD, wafers are placed in a quartz reactor, 
maintained at atmospheric or slightly reduced pressure and 
at a temperature between 650° and 750° C. Metals to be 
deposited are in the forms of gases that chemically com- 
bine on the heated substrate. For example, to prepare a 
GaAlAs layer, gallium and aluminum are present in the 
form of organic gases, generally trimethyl or triethyl 
gallium and aluminum [(CH 3 ) 3 Ga or (C 2 H 5 ) 3 Ga and 
(CH 3 ) 3 A1 or (QILJjAl] in a hydrogen carrier gas. Arsenic 
is in the form of AsH 3 in the hydrogen carrier gas. 
Dopants may also be added. The flow rates of these gases 
are carefully controlled. As the gases mix in the reactor 
and contact the hot wafers, they react to form GaAlAs and 
methane or ethane, and the GaAlAs deposits on the 
substrate wafers. 



With MBE, the GaAs substrate is mounted on a 
heating block in a reactor maintained under a vacuum, 
along with effusion cells containing the elements to be 
deposited. For a GaAlAs layer, the effusion cells would 
contain gallium, aluminum, arsenic, and dopants. The 
elements are heated to temperatures that cause them to 
evaporate. By precise opening and closing of mechanical 
shutters in front of the effusion cells, the concentration of 
each element as it deposits can be carefully controlled. 

With both MOCVD and MBE, the process may be 
repeated to build many thin layers of materials with dif- 
fering compositions. After the epitaxial layers are depos- 
ited, device manufacture can be completed through depo- 
sition of metallic and insulating layers (fig. 8). 

As with crystal growth methods, both MOCVD and 
MBE have advantages and disadvantages. MOCVD can 
coat multiple wafers at a time, whereas MBE systems can 
coat only one. MBE requires a vacuum, while MOCVD 
can be performed at atmospheric pressure. The cost of 
MOCVD equipment is approximately one-third the cost of 
MBE equipment ($250,000 compared with $800,000). 
MBE provides the most precise control over the compo- 
sition and thickness of the epitaxial layers, and it also pro- 
vides the greatest reproducibility. MOCVD uses AsH 3 
gas, which requires a room equipped with safety equip- 
ment to prevent the toxic gas from escaping. 



GBL 

GigaBit Logic 




INCHES 



Figure 8.— GaAs wafer with devices (Courtesy GigaBit Logic Inc.) 



15 



SECONDARY RECOVERY 



Because of the low yield in processing gallium to 
optoelectronic devices or ICs, substantial quantities of new 
scrap are generated during the various processing stages. 
These wastes have varying gallium and impurity contents, 
depending upon the processing step from which they 
result. GaAs-based scrap, rather than metallic gallium, 
represents the bulk of the scrap that is recycled. During 
the processing of gallium metal to a GaAs device, waste is 
generated during the GaAs ingot formation. If the ingot 
formed does not exhibit single-crystal structure or if it 
contains excessive quantities of impurities, it is considered 
to be scrap. Also, some GaAs remains in the reactor after 
the ingot is produced and may be recycled. During the 
wafer preparation and polishing stage, significant quantities 
of wastes are generated. Before wafers are sliced from the 
ingot, both ends of the ingot are cut off and discarded, 
because impurities are concentrated at the tail end of the 
ingot and crystal imperfections occur at the seed end. 
These ends represent up to 25 pet of the weight of the 
ingot. As the crystal is sliced into wafers, two types of 
wastes are generated-saw kerf, which is essentially GaAs 
sawdust, and broken wafers. When the wafers are 
polished with an abrasive lapping compound, a low-grade 
waste is generated. During the epitaxial growth process, 
various wastes are produced, depending on the growth 
method used. In LPE, metallic gallium contaminated with 
arsenic and dopant metals results, and in VPE, exhaust 
gases containing GaAs are produced. Because GaAs is a 
brittle material, wafers may break during the fabrication of 
electrical circuitry on their surfaces. These broken wafers 
also may be recycled. 

Gallium content of these waste materials ranges from 
less than 1 pet to 99.99 pet. LPE wastes normally have the 
highest gallium content, 98 to 99.99 pet. Ingot ends and 
wafers broken during processing generally contain 39 to 
48 pet gallium, VPE exhaust gases contain 6 to 15 pet 
gallium, saw kerf contains up to 30 pet gallium (wet basis), 
and lapping compound wastes contain less than 1 pet 
gallium. These wastes are contaminated with small 
quantities of many impurities, the most common being 
aluminum oxide, copper, chromium, germanium, indium, 
silicon, silicon carbide, tin, and zinc. Wafers broken 
during the fabrication of electrical circuitry also contain 



gold and silver impurities. In addition to metallic 
impurities, the scrap may be contaminated with materials 
introduced during processing such as water, silicone oils, 
waxes, plastics, and glass. 

In processing GaAs scrap, the material is crushed, if 
necessary, and then dissolved in a hot acidic solution. This 
acid solution is neutralized with a caustic solution to 
precipitate the gallium as gallium hydroxide, which is 
filtered from the solution and washed. The gallium 
hydroxide filter cake is redissolved in a caustic solution and 
electrolyzed to recover 3N to 4N gallium metal. This 
metal may be refined to 6N or 7N gallium by conventional 
purification techniques if desired. 

Some GaAs manufacturers recycle their own scrap, or 
scrap may be sold to metal traders, to a company that 
specializes in recycling GaAs, or to the GaAs manufac- 
turer's gallium supplier, who can recover the gallium and 
return it to the customer. Generally the prices com- 
manded by GaAs scrap parallel the price fluctuations of 
4N gallium metal. Also, prices are dependent on the type 
and gallium content of the scrap; saw kerf sells for a lower 
price than ingot scrap, which in turn sells for a lower price 
than metallic (LPE) scrap. 

Although GaAs scrap is an important component of the 
gallium materials flow throughout the world, it cannot be 
considered an additional long-term source of world gallium 
supply. GaAs scrap that is recycled is new scrap, which 
means that it has not reached the consumer as an end 
product and is present only in the closed-loop operations 
between the companies that recover gallium from GaAs 
scrap and the wafer and device manufacturers. Because 
this closed loop occasionally crosses international 
boundaries, it is difficult to distinguish between gallium 
recovered from scrap and virgin gallium when evaluating 
the gallium supply of an individual country. For example, 
GaAs scrap generated in the United States and Canada 
may be processed to recover 4N gallium in Canada. The 
4N gallium is shipped to Switzerland for refining to 7N 
gallium, which is then exported to the United States. In 
this situation, the gallium received in the United States 
from Switzerland appears to be a new source of supply, 
while in fact a portion of this gallium originated as GaAs 
scrap from the United States. 



16 



WORLD SUPPLY AND DEMAND 



Little information is published detailing gallium produc- quantities of gallium are exported from either the United 
tion and trade data. The United States and Japan are the States or Japan, but significant trade in GaAs occurs, 
only countries for which detailed data are available. Also Some GaAs scrap is exported from the United States to 
in many cases, no distinction is made in published figures the Federal Republic of Germany for gallium recovery, 
between virgin, recycled, and purified gallium. As an and Japan is believed to export significant quantities of 
example, the United States ships some GaAs scrap to the GaAs substrate wafers to the United States. However, 
Federal Republic of Germany for gallium recovery, and because the value of these items is very small when the 
the recovered gallium is returned to the United States. value of the entire U.S. trade is considered, they are not 
This gallium may be counted twice as a part of the domes- classified separately. So the trade patterns of these mate- 
tic supply. Or, one country recovers virgin gallium and rials cannot be quantitatively determined, 
ships it to a second country for refining to 7N gallium. In addition to gallium metal and GaAs trade, the 
Each country may count this as production, thus doubling United States imports many of its consumer electronics 
the quantity of gallium that appears to be available. Con- goods and automobiles. Many of these items, such as 
sequently, determination of gallium supply-demand figures compact disk players, televisions, calculators, and video 
is subject to significant interpretation. cassette recorders, contain GaAs components in the form 

of LEDs and laser diodes. Here again, significant quan- 

PRODUCTION tides of gallium compounds may be imported, but cannot 

be quantitatively determined. 

Tables 3 and 4 show estimates of both primary and sec- 
ondary gallium production. These figures were derived DOMESTIC DEMAND 
from U.S. production data, published by the Bureau of 

Mines; U.S. import data, supplied by the Department of U.S. supply-demand relationships, shown in table 7, 

Commerce; and production and import data for Japan, indicate that most of the domestic demand for gallium has 

published in RoskilTs Letter From Japan. Because most been supplied by imports. Before 1983, the Aluminum Co. 

of the world's gallium demand centers in Japan and the of America (Alcoa) and Eagle-Picher Industries Inc. 

United States, these sources are believed to provide data recovered primary gallium in the United States. But after 

on about 85 pet of the gallium produced in the world. 1983, no primary gallium was produced until 1986, when 

Musto Explorations began recovering a small quantity of 

TRADE gallium from its mine in Utah. 

Over 90 pet of the gallium consumed in the United 

Import data for the United States and Japan are shown States is classified as "instruments." This category includes 

in tables 5 and 6. Historically, the United States has gallium consumed in optoelectronic devices, in ICs, and in 

received most of its gallium from France, the Federal some research and development activities. The remainder, 

Republic of Germany, and Switzerland, while Japan's prin- classified as "other," consists of gallium consumed in other 

cipal import sources have been China, France, and the research and development activities and in specialty alloys. 

Federal Republic of Germany. No data are published Optoelectronic devices represent most of the gallium 

separately detailing gallium exports from the United demand in the United States. 
States, Europe, or Japan. It is believed that no significant 

Table 3. - World primary gallium production" 

(Kilograms) 

Country 1980 1981 1982 1983 1984 1985 1986 1987 

China 3,000 3,400 2,600 5,100 3,500 5,000 6,000 6,000 

Czechoslovakia 500 1,650 1,700 2,000 2,500 3,300 3,000 3,200 

France 4,300 4,600 3,700 7,000 8,500 9,500 15,500 14,000 

Germany, Federal Republic of 2,300 3,000 4,000 5,300 6,000 5,500 7,000 7,000 

Hungary 1,500 1,500 2,000 3,000 3,000 2,800 3,200 3,000 

Japan 3,000 3,000 3,000 3,000 10,000 10,000 10,000 5,000 

Norway 500 

United States 3,000 1,500 1,560 l '750 W 

Total 17,600 18,650 18,560 25,400 33,500 36,100 45,450 ^^OO 

'Estimated. W Withheld to avoid disclosing individual company proprietary data. 
'Reported figure. 
2 Excluding U.S. production. 



17 



Table 4. - World secondary gallium production 
(Kilograms) 



e 1 



Country 

Canada 

Germany, Federal Republic of 

Japan 

United Kingdom 

United States 

Total 

'Estimated. 
*New scrap only. 



1980 



1981 



1982 



1983 



1984 



1985 



1986 



1987 
























500 


500 


700 


1,000 


2,100 


1,500 


1,500 


3,000 


5,000 


4,000 


5,000 


7,000 


4,000 


9,000 


200 


300 


800 


1,000 


1,000 


1,000 


1,500 
























3,700 



5,800 



5,500 



7,000 



10,100 



6,500 



12,000 



5,000 
1,500 
7,000 
1,500 
2,400 



17,400 



Table 5. - U.S. /gallium imports for consumption, by country 

(Kilograms) 

Country 1977 1978 1979 1980 1981 1982 1983 

Belgium-Luxembourg 200 

Canada 276 75 450 1,449 589 379 279 

China 409 916 500 

Congo 

Czechoslovakia 53 

France 232 386 480 829 

Germany, Federal Republic of ... 774 748 218 561 585 1,448 918 

Hungary 37 59 

India 10 

Italy 349 98 

Japan 41 13 48 146 

Malaysia 100 2 

Netherlands 41 

New Zealand 

Singapore 

Spain 148 

Suriname 

Sweden 1 

Switzerland 1,485 2,628 5,498 3,444 2,679 2,429 4,154 

Taiwan 11 

United Kingdom 133 41 56 70 267 468 

Total 2,884 3,721 6,401 6,175 5,536 5,199 7,294 

Source: U.S. Department of Commerce. 



1984 



1985 



1986 



1987 






55 








1 


3 


98 


107 


400 














10 




















2,449 


1,563 


8,231 


6.364 


1,554 


1,423 


2,740 


1,215 


168 





17 

















1 








13 


89 


105 


123 


451 


5 


40 








131 


50 








132 




















21 

















30 





96 





201 


5 





4,088 


4,268 


5,640 


4,081 





50 








651 


163 


348 


142 



9,669 7,961 17,202 12,490 



Table 6. - Japanese/gallium imports, by country 
(Kilograms) 



Country ^980 1981 

Canada 

China 2,500 2,400 

Czechoslovakia 500 

France 10 2,000 

Germany, Federal Republic of .... 1,200 1,800 

Hungary 10 600 

Switzerland 1 ,400 300 

U.S.S.R _0 0_ 

Total 5,120 7,600 

Source: Roskill's Letter From Japan and Rare Metals News. 



1982 



1983 



1984 



1985 



1986 



1987 





2,600 
1,260 
1,400 
2,100 
1,600 
120 






4,600 

480 

2,800 

3,720 

2,300 

100 

200 





2,800 

900 

3,100 

5,450 

1,500 

85 






4,000 
2,285 
5,264 
3,200 
1,800 
50 





9,080 



14,200 



13,835 



16,599 



300 
5,100 

450 
2,700 
4,200 

750 

100 




13,600 



300 
2,000 
1,100 
5,600 
4,900 
1,500 

740 




16,140 



18 



Table 7. - Gallium supply-demand relationships, 1 977-87 
(Kilograms) 





1977 1978 


1979 1980 1981 1982 1983 


1984 


1985 


1986 


1987 


WORLD PRODUCTION 


United States 


W e 5,500 


e 2,600 e 3,000 e 1,500 e 1,560 e 
e 9,500 e 14,600 e 17,150 c 17,100 e 25,400 


e 

e 33,500 




e 36,100 


750 

e 44,700 


W 


Rest of world 


W e 6,650 


e 38,700 






Total' 


12,420 12,200 


12,100 17,600 18,650 18,660 25,400 


33,500 


36,100 


45,450 


^JOO 


COMPONENTS AND DISTRIBUTION OF U.S. SUPPLY 



e 2,600 
6,401 
e 2,000 



e 3,000 
6,175 
e 1,800 



e 1,500 

5,536 

e 1,900 



e 1,560 
5,199 
e 1,900 



•11,001 c 10,975 8,936 8,659 c 9,149 11,499 8,887 19,158 



e 1,900 

e 265 

8,810 



Components of U.S. supply: 

Production W c 5,500 

Imports 2,884 3,721 

Industry stocks, Jan. 1 _ W e 1,950 

Total 11,054 11,221 

Distribution of U.S. supply: 

Industry stocks, Dec. 31 e 1,950 e 2,000 

Exports e 315 e 313 

Demand 8,789 8,908 

7,965 8,305 

824 603 

8,789 8,908 

Estimated. NA Not available. W Withheld to avoid disclosing company proprietary data. 
'Excluding U.S. production. 

STRUCTURE OF THE INDUSTRY 



e o 

7,294 
1,855 



e 
9,669 
1,830 





7,961 

926 



750 

17,202 

1,206 



e 1,800 

e 151 

9,050 



e 1,900 

e 226 

6,810 



e 1,855 

e 157 

6,647 



1,830 926 

e 894 e 3,513 

6,425 7,060 



W 

12,490 

813 



W 



1,206 813 732 

c 285 e 2,302 NA 

7,396 16,043 10,729 



U.S. DEMAND PATTERN 


Instruments 

Other 


7,965 

824 


8,305 
603 


8,398 8,105 6,299 
652 705 51 1 


6,124 
523 


5,915 
510 


6,320 
740 


7,071 
325 


14,920 
1,123 


10,397 
332 


Total U.S. demand .... 


8,789 


8,908 


9,050 8,810 6,810 


6,647 


6,425 


7,060 


7,396 


16,043 


10,729 



Because gallium is a byproduct metal and undergoes 
many refining and processing stages before a marketable 
product is produced, gallium is truly an international 
business. Most bauxite is mined in Australia, Africa, and 
South America, while gallium recovery and refining are 
currently centered in Europe. GaAs wafer and device 
fabrication is concentrated in the United States and Japan. 

Many gallium producers have the facilities to recover 
3N and 4N gallium and refine it to higher purity. Some 
gallium producers also have scrap recycling facilities. 
Table 8 shows current and projected capacities for each 
company that is involved in recovering, recycling, or 
purifying gallium metal, or has announced plans to 
construct new facilities. Virgin and recycle gallium plants 
produce 3N to 4N gallium, while purification plants yield 
gallium of 6N to 8N purity. Because of the nature of 
gallium processing, the only figures that should be 
considered when evaluating the long-term availability of 
gallium are the virgin gallium capacities. 

GALLIUM RECOVERY, RECYCLE, AND 
PURIFICATION 

Australia 

Although gallium is not currently recovered in 
Australia, Rhone-Poulenc of France plans to construct a 
50,000-kg/yr gallium extraction plant in Pinjarra, Western 
Australia, to be completed by the second half of 1988. 
The gallium source for the operation will be the Bayer 
liquors generated by Alcoa of Australia Ltd.'s alumina 
refinery at the same location, which uses locally mined 
bauxite as its feed source. When this plant is completed, 
it will be the largest gallium extraction plant in the world, 
producing 4N gallium metal. 



Canada 

Alcan Aluminium Ltd. completed a 10,000-kg/yr gal- 
hum recycling plant at Kingston, Ontario, in early 1986. 
GaAs scrap from both the United States and Canada is 
used as feed for the plant, to produce 4N gallium. Alcan 
also is constructing a new facility at its Jonquiere, Quebec, 
alumina refinery to produce virgin gallium, which is 
expected to be completed in 1988. The alumina plant uses 
bauxite from Brazil, Guinea, and Guyana as feed material. 
When the plant is completed, its capacity will be 4,000 
kg/yr of 4N gallium metal. 

Cominco recovers gallium at a 4,000-kg/yr refinery in 
Trail, British Columbia. Although the company also 
refines zinc concentrates at the same location, it does not 
recover gallium from these concentrates. Instead crude 
gallium metal, gallium oxide, scrap, and flue dust 
purchased from outside sources are used as plant feed to 
produce 6N to 7N gallium metal. 

China 

Gallium metal of 3N to 4N purity is recovered in 
Shangdong at the Nanding alumina plant. Bauxite is 
mined locally, and the gallium extraction plant has a 
capacity of 8,000 kg/yr. Most of the gallium produced in 
China is shipped to Japan for refining to 6N and 7N metal. 

Czechoslovakia 

Gallium metal is produced at the Ziar nad Hronom 
alumina refinery, which uses bauxite from Hungary and 
Yugoslavia as its raw material. At the 3,000-kg/yr plant, 
3N to 4N gallium metal is produced, and most of the 



19 



Table 8. - World gallium plant capacities' 



Plant location 



Ownership 



1987 



Yearend capacity, mt 



1988 



1989 



1990 



Primary (virgin) gallium extraction plants: 

Australia 

Canada 

China 

Czechoslovakia 

France 

Germany, Federal Republic of 

Hungary 

India 

Japan 

Do 

Norway 

United States 

Do 

Do 



Total 



Secondary gallium recovery plants: 
Canada 

Do 

France 

Germany, Federal Republic of . . 

Do ' 



Japan 

Do 

Do 

Do 

Do 

United Kingdom 
United States . . 



Total 

Gallium purification plants: 
Canada 

Do 

France 

Germany, Federal Republic of 
Japan 

Do 

Switzerland 

United Kingdom 

United States 

Do 



Total 



Rhone-Poulenc SA 

Alcan Aluminium Ltd 

Shangdong Aluminium Co 

Czechoslovakian Government . . . 

Rhone-Poulenc S.A 

Ingal International Gallium GmbH 

Hungarian Aluminium Co 

Madras Aluminium Co 

Dowa Mining Co 

Sumitomo Chemical Co. Ltd. . . . 

Elkem A/S 

Eagle-Picher Industries Inc 

Musto Explorations Ltd 

Sulzer Brothers Inc 






8 
3 
20 
12 
4 

A 

7 
10 
5 
3 
9 




81 



Alcan Aluminium Ltd 

Comjnco Ltd 

Societe Miniere et Metallurgique de Penarroya 

Ingal International Gallium GmbH 

Preussag AG Metall 

Dowa Mining Co 

Rasa Industries Ltd 

Sumitomo Chemical Co. Ltd 

Sumitomo Metal Mining Co. Ltd 

Ote Metal Co 

Mining and Chemical Products Ltd 

Recapture Metals Inc 



10 


ft 

6 
8 

2 
3 
5 
3 
6 
3 
4 



50 



Alcan Aluminium Ltd 

Comino Ltd 

Rhone-Poulenc S.A. 

Ingal International Gallium GmbH . 

Dowa Mining Co 

Sumitomo Chemical Co. Ltd 

Alcan Aluminium Ltd 

Mining and Chemical Products Ltd. 

Eagle-Picher Industries Inc 

Rhone-Poulenc S.A 





4 

20 

15 

7 
10 
10 

3 

7 


~76~ 



50 
4 
8 
3 
20 
12 
4 

C) 
7 

10 
5 
3 
9 

15 



150 



10 


C) 

6 
8 

2 
3 
5 
3 
6 
3 
4 



50 





4 
20 
20 

7 
10 
10 

3 

7 
50 



131 



50 
4 
8 
3 
20 
15 
8 

C) 

7 
10 
5 
3 
9 
15 



157 



10 


10 
6 
8 
2 
3 
5 
3 
6 
3 
4 



60 



5 

4 

20 

20 

7 

10 

10 

3 

7 

50 



136 



50 
4 
8 
4 

20 

20 
8 
3 
7 

10 
5 
3 
9 

15 



166 



10 
4 

10 
6 
8 
2 
3 
5 
3 
6 
3 
4 



64 



5 

4 

20 

20 

7 

10 

10 

3 

7 

50 

136 



Estimated. Less than 1/2 unit. 



gallium is exported to Japan for purification. Czechoslo- 
vakia plans to expand this plant's capacity to 4,000 kg/yr 
by 1990. 

France 

Rhone-Poulenc operates the world's largest gallium 
extraction plant at Salindres, with a capacity of 20,000 kg 
of gallium per year. Bayer liquor from Pechiney's 
Gardanne alumina refinery, which recovers alumina from 
bauxite mined locally and in Guinea, is used as feed for 
the gallium extraction plant. Rhone-Poulenc produces 4N 
gallium, which is then further refined to 6N and 7N 
gallium at Salindres. The bulk of this high-purity gallium 
is shipped to the United States and Japan. 

Societe Miniere et Metallurgique dc Penarroya SA. 
plans to increase its capacity for recycling GaAs scrap to 
10,000 kg/yr by 1989. Penarroya already has a small 



capability to recover gallium from scrap at its plant at 
Noyelles-Godault. 

Federal Republic of Germany 

Ingal International Gallium GmbH operates two 
gallium recovery plants at Schwandorf and Lunen with a 
combined extraction capacity of 12,000 kg/yr. VAW's two 
alumina plants at the same locations, which recover 
alumina from bauxite mined in Australia and Guinea, 
supply Bayer liquor to Ingal's gallium extraction circuit. 
VAW's alumina refinery in Lunen is scheduled to close in 
1988, but Ingal plans to construct a new 20,000-kg/yr plant 
in grade as a replacement, which is expected to be fully 
operational by mid-1989. In addition to extracting virgin 
gallium, Ingal also purifies its gallium to 6N to 7N purity 
at Schwandorf and recovers gallium from GaAs scrap. 



20 



Most of the high-purity gallium is exported to the United 
States and Japan. 

Preussag AG Metall operates an 8,000-kg/yr gallium 
recycling facility in Langelsheim to recover 3N to 4N 
gallium from GaAs scrap. 

Hungary 

Virgin gallium is extracted at Hungarian Aluminium 
Corp.'s facility in Ajka. Bayer liquor from the company's 
alumina refinery, which uses locally mined bauxite as its 
raw material, is used as the gallium source for the 4,000- 
kg/yr plant. Gallium of 3N to 4N purity is recovered in 
Hungary; most of it is shipped to Japan for refining. In 
1986, Hungarian Aluminium announced that it planned to 
double the capacity of its plant by 1988. 

India 

Madras Aluminium Co. Ltd. began pilot-scale 
production of virgin gallium metal in late 1986 at its plant 
in Mettur, Tamil Nadu. The company's alumina refinery 
at the same location supplies the Bayer liquor feed stock, 
using locally mined bauxite as the alumina plant's raw 
material source. 

Japan 

Two companies in Japan, Dowa Mining and Sumitomo 
Chemical, produce virgin gallium, recover gallium from 
scrap, and produce 6N to 7N gallium metal for the 
Japanese market. Dowa Mining recovers gallium from 
zinc residues at its 7,000-kg/yr gallium extraction plant in 
Akita, Honshu. Zinc residues are generated at the Akita 
Zinc Co. Ltd. plant, which is 52 pet owned by Dowa 
Mining, from zinc ores mined at Akita Zinc's Uchinotai 
and Hanaoka Mines. Sumitomo Chemical recovers gal- 
hum at its 10,000-kg/yr plant in Niihama, Shikoku. Before 
the closure of its last operating alumina refinery in 
October 1986, Sumitomo Chemical used Bayer liquors 
from the alumina plant as its source of gallium. Both 
Dowa Mining and Sumitomo Chemical operate gallium 
purification facilities, where they produce 6N to 7N metal. 
In addition to refining their own productions, both 
companies purify imported 3N to 4N gallium, principally 
from China, Czechoslovakia, and Hungary. 

Rasa Industries Ltd. operates plants at Miyako and 
Osaka that recover 3N to 4N gallium from GaAs scrap. 
Combined plant capacity is estimated to be 3,000 kg/yr. 
Two other companies began operating secondary gallium 
recovery facilities in 1987. Ote Metal Co., a subsidiary of 
Mitsubishi Metal Corp., began recovering 3N to 4N gal- 
lium from GaAs scrap at its 6,000-kg/yr plant at the 
Onahama refinery in January. Sumitomo Metal Mining 



Co. Ltd. began operating a 3,000-kg/yr secondary gallium 
recovery facility in Niihama in July. 

Norway 

Elkem began operating a newly constructed gallium 
extraction plant at its Bremanger ferroalloy plant site in 
July 1987. Aluminum smelter flue dusts from primary 
aluminum refineries in Mosjoen and Tyssedal, containing 
about 0.5 pet gallium, are used as the source material for 
the 5,000-kg/yr plant. Only small quantities of 3N to 4N 
gallium have been produced at this facility. 

Spain 

Early in 1988, Rhone-Poulenc announced that it had 
signed an agreement with the Spanish Government to 
purchase the entire output of gallium-containing residues 
from the Aluminia Espanola SA. (Inespal) alumina 
refinery in San Ciprian. Although no date has been given 
for the start of construction, Rhone-Poulenc plans to 
construct a gallium extraction facility near San Ciprian. 
The residues are estimated to contain up to 30,000 kg/yr 
of gallium, but the plant capacity has not been stated. 

Switzerland 

Alcan operates a 10,000-kg/yr gallium purification plant 
in Rorschach, which it purchased from Swiss Aluminium 
Ltd. in 1985. The Rorschach plant produces gallium of 6N 
to 8N purity using 3N to 4N gallium recovered from scrap 
at the company's plant in Canada as the feed material. 
Most of Alcan's production is shipped to the United 
States, with a small quantity exported to Japan. 

U.S.S.R. 

Although no data are available to determine quantities 
and locations of plants that recover gallium, it is believed 
that the U.S.S.R. recovers, purifies, and consumes 
significant quantities of gallium for IC production. In 
1986, it was announced that the U.S.S.R. plans to increase 
its production and usage of gallium, according to the 
1986-90 5-year plan. 

United Kingdom 

Mining and Chemical Products Ltd. operates a 3,000- 
kg/yr gallium recycling facility in Alperton, Wembley, to 
recover gallium from GaAs scrap generated at its 
electronic materials division. In addition to recovering 3N 
to 4N gallium from scrap, the company has facilities to 
produce high-purity gallium for the U.S. and European 
markets. 



21 



United States 

St. George Mining operates a mine and processing plant 
near St. George, UT, to recover gallium contained in iron 
oxide minerals that remained at an abandoned copper 
mine. Gallium metal of 5N purity was produced at the 
9,000-kg/yr plant until September 1987, when the plant 
was temporarily closed for repairs. In mid-1988, St. 
George Mining field for bankruptcy. Much of the gallium 
to be produced was expected to be shipped to Eagle- 
Picher's plant in Quapaw, OK, for refining to 6N to 7N 
purity. Eagle-Picher has a 3,000-kg/yr capacity to recover 
gallium from zinc residues generated at its Quapaw plant, 
but has not produced virgin gallium since 1982. However, 
the company does produce 4N, 5N, and 7N gallium metal 
from gallium concentrates and GaAs and GaP scrap. 

Sulzer Brothers Inc. plans to complete construction of 
a 15,000-kg/yr gallium extraction facility by the end of 
1988. The plant, in Gramercy, LA, will obtain Bayer 
liquor from Kaiser Aluminum & Chemical Corp.'s alumina 
refinery at the same location, which uses bauxite from 
Jamaica as its feed source. The first 2 years' production 
is scheduled to be shipped to Europe in the form of a 
gallium chloride solution to be used in a solar neutrino 
capture experiment. After this commitment has been 
fulfilled, a decision will be made concerning the plant's 
future gallium production. 

Rhone-Poulenc plans to construct a 50,000-kg/yr 
gallium purification plant at Freeport, TX, by 1988. The 
plant is expected to use the 3N to 4N gallium recovered at 
the company's plant in Australia as feedstock. The 6N to 
7N gallium metal produced at the refinery is expected to 
be used by the United States. 

Recapture Metals Inc. began operating a 4,000-kg/yr 
gallium recycling facility in Blanding, UT, in 1986. 



Although the company can produce gallium with a purity 
of 6N to 7N, most of its product is 3N to 4N gallium. 

HIGH-PURITY ARSENIC PRODUCTION 

Arsenic is recovered as arsenic trioxide in about 20 
countries from the smelting or roasting of nonferrous 
metal ores or concentrates. Arsenic metal, which accounts 
for only about 3 pet of the world demand for arsenic, is 
produced by the reduction of arsenic trioxide. Commer- 
cial-grade arsenic metal, 99-pct-pure arsenic, is produced 
in only a few countries, and this grade accounts for the 
majority of arsenic metal production. High-purity arsenic, 
4N purity or greater, for use in the semiconductor industry 
is produced by about 10 companies. Furukawa Co. Ltd. in 
Japan and Preussag in the Federal Republic of Germany 
are believed to be the world's largest producers, with 
reported capacities of 30,000 kg/yr and 15,000 kg/yr, 
respectively. Other high-purity arsenic producers include 
Cominco in Canada, Mitsubishi Metal and Rasa Industries 
in Japan, and Johnson Matthey Ltd. and MCP Electronic 
Materials Ltd. in the United Kingdom. 

GALLIUM ARSENIDE INGOT, WAFER, AND 
DEVICE MANUFACTURERS 

Table 9 lists companies involved in various phases of 
GaAs wafer and device manufacture. As is evident from 
the number of companies listed for these countries, most 
of the advanced GaAs manufacturing occurs in the United 
States and Japan. Some companies are fully integrated 
from GaAs ingot manufacture through device manufacture, 
while others make either wafers or devices. 



Table 9. - Gallium arsenide Ingot, wafer, and device manufacturers 

Country and company Ingot and wafer manufacture Epitaxy Device manufacture 

LEC HB LPE VPE MOCVD MBE Optoelectronic Analog Digital 

Canada: Cominco Electronic x 

Materials Ltd. 
France: 

Picogiga x 

The Philips Group x 

Thomson CSF x x 

Germany, Federal Ftepublic of: 

Siemens AG x x x x 

Wacker Chemitronic AG x x 



22 



Table 9. • Gallium arsenide Ingot, wafer, and device manufacturers— Continued 



Country and company Ingot and wafer manufacture Epitaxy Device manufacture 

LEC HB LPE VPE MOCVD ~MBE Optoelectronic Analog Digital 

Japan: 

Dowa Mining Co x 

Fujitsu Ltd x x 

Furukawa Co. Ltd x 

Hitatchi Cable Ltd x x x x 

Hitatchi Manufacturing Co. Ltd. . x x 

Iwaki Co. Ltd x 

Japan Victor Corp x 

Matsushita Electric Corp x x 

Mitsubishi Electric Corp x x 

Mitsubishi Metal Corp x x x 

Mitsubishi Monsanto Chemical x x x x 

Co. Ltd. 

NEC Corp x x 

Nippon Mining Co. Ltd x 

Oki Electric Industry Co. Ltd. ... x 

Sanyo Electric Co. Ltd x 

Sharp Corp x 

Shin-Etsu Semiconductor Corp. x 

Showa Denko K.K. . x 

Stanley Electric Co. Lid x 

Sumitomo Electric Industries Ltd. x x x x 

Sumitomo Metal Mining Co. Ltd. x x 

Toshiba Corp x x 

Sweden: Semitronics AB x 

United Kingdom: 

General Electric Co. (U.K.) .... x x x x x 

ICI Wafer Technology x 

MCP Electronic Materials Ltd. . . x 

Plessey PLC x x x 

United States: 

Airtron Div. of Litton Industries . x 

Anadigics Inc x x x 

Applied Solar Energy Corp x x 

AT&T Bell Laboratories x x x x 

Bertram Laboratories x 

Crystal Specialties Inc x x x x 

Epitronics Corp x x 

Ford Microelectronics Div. of x x 

Ford Motor Co. 

General Electric Co x x 

General Instrument Corp ■ x 

GigaBit Logic Inc 

Harris Microwave Semiconductor x 

Corp. 

Hewlett Packard Inc x x x x 

Honeywell Inc x x 

Hughes Aircraft Co x 

IBM Corp 

ITT Corp x 

Kopin Corp x 

Laser Diode Inc x 

M/A-Com Inc x 

McDonnell Douglas Corp x 

Morgan Semiconductor Div. of x x x 

Ethyl Corp. 

Motorola Inc x x 

Pacific Monolithics Inc x x 

Rockwell International Corp. . . . x x x x x 

Siemens Corp x x 

Spectrum Technology Corp. ... x 

Spire Corp x x 

Texas Instruments Inc x x x x 

TriQuint Semiconductor Inc. ... x x 

TRW Inc x x x x 

Varo Inc x x 

Vitesse Semiconductor Corp. . . x 

Westinghouse Electric Co x x x x 



x x 

X 

X X 

X X 

X X 
X X 

X XX 
X X 

X XX 
X 

X X 



23 



RESEARCH AND DEVELOPMENT 



Considerable research is being done concerning all 
phases of gallium extraction, GaAs material properties, 
and GaAs-based device manufacturing. Because GaAs IC 
manufacture is still in the developmental stage, much of 
the research activity centers on designing and manufac- 
turing devices. 

The Department of Defense sponsors a great deal of 
gallium research through the Defense Advanced Research 
Projects Agency (DARPA) and the National Aeronautics 
and Space Administration (NASA) as well as through the 
service branches' laboratories. Over the past few years, 
DARPA's focus in funding projects has been to increase 
the efficiency of processing GaAs devices. Although a 
variety of microwave and digital ICs have been fabricated 
from GaAs, many of these were prototype devices. 
Projects funded through DARPA were principally designed 
to increase the limited production of the prototype devices 
to full-scale manufacturing. Improving the manufacturing 
process may allow more complex ICs to be developed with 
increased radiation resistance and faster speed. By con- 
trast, NASA is principally investigating optoelectronic 
devices, particularly solar cells. NASA's main thrust is to 
increase the energy efficiency and reduce the cost of 
GaAs-based solar cells. 

In 1986, the Department of Defense announced that it 
would begin a $135 million program to develop MMICs 
for military electronic applications. The program, expected 
to begin in 1988, is called Mimic for Microwave/Millime- 
ter Wave Monolithic Integrated Circuit. Mimic would pro- 
vide funds for companies that are already involved in 
GaAs research to accelerate their activities. 

Most of the companies that are involved in the 
commercial GaAs market, both in optoelectronic devices 
and ICs, are involved in the development of devices that 
optimize the properties of GaAs. Among the new devices 
that are being developed are the high-electron-mobility 
transistor (HEMT), heteroj unction bipolar transistor 
(HBT), ballistic transistor, and quantum-well laser. 
HEMTs consist of an undoped GaAs substrate with a thin 
epitaxial layer of silicon-doped GaAlAs on top. When an 
electric current is passed through the HEMT, electrons 
from the impurity atoms in the GaAlAs layer fall into the 
GaAs layer, where they move very fast. HBTs operate in 
essentially the same manner, but the GaAlAs layer is more 
highly doped. Both HEMTs and HBTs could increase 
signal processing speed in MMICs and digital ICs. A 
ballistic transistor is basically a sandwich structure with 
two GaAlAs layers on both sides of an ultrathin GaAs 
layer. As in an HEMT device, electrons from the GaAlAs 
layer fall into the GaAs layer and pick up speed. But 
because the GaAs layer is so thin, electrons pass through 
the GaAs layer and into the second GaAlAs layer without 
slowing down. This enhanced electron movement could 



increase the speed of digital ICs and would allow MMICs 
to operate at high frequencies. The quantum-well laser is 
fabricated in the same way and with the same materials as 
the ballistic transistor, but instead of passing through the 
GaAs layer, electrons are trapped in this layer. By 
confining the charge carriers to this very small area, the 
chance is increased that they will recombine to emit light. 
Consequently, this structure increases the amount of light 
generated for a specific electrical signal (<5). Development 
of these new devices has been made possible with the 
advent of MOCVD and MBE, which are capable of 
depositing ultrathin layers on a substrate. 

With increased emphasis on developing new devices, 
demands have been placed on the GaAs substrate 
manufacturers to supply better quality and more uniform 
substrates. Consequently GaAs wafer manufacturers have 
been refining their crystal growth techniques to produce 
material with fewer defects, to improve the yield from 
gallium and arsenic metals to GaAs wafers, and to scale up 
production. At the same time, wafer manufacturers are 
trying to produce larger diameter wafers that ultimately 
could increase the yield from wafer to device. 

Companies involved in epitaxial growth are also working 
to improve properties such as the uniformity in the 
thickness and composition of the epitaxial layers. Recently 
metal-organic molecular beam epitaxy (MOMBE), also 
referred to as chemical beam epitaxy, has been developed 
to combine the advantages of MOCVD and MBE. These 
advantages include superior epitaxial layer thickness and 
uniformity, defect-free surfaces, the ability to grow layers 
on more than one wafer at a time, and the ability to 
introduce and control phosphorus atoms for optoelectronic 
device fabrication. MOMBE was introduced in early 1987. 

Work is also being done on combining GaAs with other 
materials to take advantage of the best qualities in each 
material. Prototypes of GaAs epitaxial layers grown on 
silicon substrates were recently produced, and sample 
quantities have been shipped to customers for testing. By 
using GaAs layers on a silicon wafer, the superior 
structural properties of silicon can be combined with the 
electrical and optical properties of GaAs. Larger, more 
durable wafers can be produced with light-emitting 
properties and increased radiation resistance. GaAs can 
be deposited by MOCVD or MBE over the entire silicon 
wafer, called blanket epitaxy, or islands of GaAs can be 
epitaxially deposited on the silicon wafer, called selective 
epitaxy. Wafers produced by blanket epitaxy could replace 
bulk GaAs wafers for GaAs MMICs and digital ICs. 
Wafers produced by selective epitaxy can combine silicon 
ICs with GaAs optoelectronic devices, GaAs MMICs, or 
GaAs digital ICs. Blanket epitaxial wafers would require 
less gallium than that consumed in the fabrication of bulk 
GaAs wafers, and selective epitaxial wafers would allow 



24 



GaAs to be used in areas in which its use is not currently 
feasible. 

In solar cells, where GaAs has not supplanted silicon to 
any great degree, epitaxial deposition of GaAs layers on 
germanium substrates may represent a hybrid substitute 
material for silicon. GaAs is fragile and can only be 
deposited in thick layers on a GaAs substrate. This puts 
GaAs at a disadvantage in comparison with silicon, which 
is sturdy and can be epitaxialry grown in thinner layers. 
Germanium substrates are stronger and less costly than 
GaAs substrates, and GaAs epitaxial layers can be grown 
thinner using MOCVD. Consequently the increased 
energy efficiency and radiation resistance of GaAs solar 
cells can be exploited, while reducing the total weight of 
GaAs-based solar cells. While providing the same power 
as silicon solar cells, GaAs-on-germanium solar cells can 
be made smaller, which allows a satellite to carry a larger 
payload. 

By continuing to ,push the limits of GaAs technology, 
researchers have also developed the optical equivalent of 
the transistor, a GaAs-based IC that controls light in the 



same manner a transistor controls electrical current. 
Thousands of alternating layers of GaAs and GaAlAs, 
each 40 atoms thick, are used in the construction of the 
IC. When a voltage is applied, the material becomes 
transparent, allowing a laser beam to shine through. A 
second, less powerful laser beam concentrates the 
electrical voltage in certain layers, which become opaque. 
Thus the second laser beam controls the transmission of 
the first laser beam. The outgoing light beam from one 
device can then be used as an input for a second device. 
Development of these devices could be a step in 
developing an optical computing device that would use 
light to transmit information rather than using electrical 
power. 

Basic research is being performed on the extraction of 
gallium from nontraditional source materials. The Bureau 
of Mines has investigated the extraction of gallium 
from phosphorus flue dust and low-grade domestic 
resources (7-8). Work is also being done by private firms 
to recover gallium from coal fly ash and phosphorus flue 
dust. 



LEGISLATION AND GOVERNMENT PROGRAMS 



Historically, gallium has not been impacted by 
legislative action, except for transportation requirements. 
In 1976, the U.S. Department of Transportation classified 
gallium as a hazardous material for purposes of transpor- 
tation. The amendment to the regulations prohibits trans- 
portation of liquid gallium aboard aircraft and specifies 
requirements for packaging solid gallium for aircraft trans- 
port and solid and liquid gallium for surface transport (9). 

Tariff rates for gallium and gallium oxide are shown in 
table 10. Under the proposed United States-Canada 



Free Trade Agreement, tariffs for gallium metal traded 
between the two countries will be removed on January 1, 
1993. 

Table 10. - U.S. Import duties for gallium, January 1, 1989 



Item Number Most favored nation 

(MFN) 



Gallium 
oxide. 
Gallium metal 8112.91.0000 



2825.90.5000 3.7 pet ad valorem 



do 



Non-MFN 

25.0 pet ad 
valorem. 
Do. 



STRATEGIC FACTORS 



Despite the fact that gallium is currently being used in 
some sophisticated military and satellite systems and is 
planned to be incorporated into additional systems, it has 
not been designated as a material to be added to the 
National Defense Stockpile. In 1986, Government and 
private agencies assessed the need to stockpile gallium, but 
because construction of additional gallium extraction plants 
is planned in North America, it was determined that in the 
event of a national emergency, gallium supplies would be 
adequate. If consumption increases dramatically over the 
next few years, it is likely that this assessment would be 
reevaluated. 

Although import dependence for gallium cannot be 
calculated according to the Bureau's formula, by 
comparing the U.S. production to the U.S. demand, it is 
apparent that the United States is highly dependent on 
imports to meet its needs. This import dependence is 
likely to continue because there is no planned construction 



of gallium extraction plants in the United States that would 
increase the commercial supply. Musto Explorations' 
existing extraction plant in Utah was operating at a 
significantly reduced capacity before its closure, and the 
gallium output of Sulzer Brothers plant under construction 
in Gramercy, LA will be shipped to Europe for at least 
2 years. 

With the rapid technological progress, especially in 
GaAs IC development, the status of world supply and 
demand is changing dramatically. GaAs has advanced 
from a laboratory curiosity, a decade or so ago, to a 
material with distinct applications and almost no effective 
substitutes at present. Development of fiber optic 
telecommunications systems, the advent of sophisticated 
electronic military warfare, the widespread use of 
consumer electronics, and the need to process vast 
quantities of data in the shortest time possible have 
provided the impetus for implementing the large number 



25 



of GaAs research and development programs. By 
continuing to push the limits of GaAs technology, its 
applications have expanded. At the same time, continuing 
research into developing other "high-tech" materials, such 



as InP, superconductors, and organic polymer semicon- 
ductors, may yield materials with properties superior to 
those of GaAs. Development of these potential substitutes 
could radically alter the future of GaAs. 



REFERENCES 



1. Zwiebel, K. Photovoltaic Cells. Chem. and Eng. News, v. 64, 
No. 27, July 7, 1986, pp. 34-48 

2. Katrak, F. E, and J. C. Agarwal. Gallium: Long-Run Supply. 
J. Met., v. 33, No. 9, Sept. 1981, pp. 33-36. 

3. Beja, M. Method of Extracting Gallium Oxide From Aluminous 
Substances. U.S. Pat. 2,574,008, Nov. 6, 1951. 

4. de la Breteque, P. Method of Recovering Gallium From an 
Alkali Aluminate Lye. U.S. Pat. 2,793,179, May 21, 1957. 

5. Frensley, W. R Gallium Arsenide Transistors. Sci. Am., v. 257, 
No. 2, Aug. 1987, pp. 80-87. 

6. Brody, H. Ultrafast Chips at the Gate. High Technol., v. 6, No. 
3, Mar. 1986, pp. 28-35. 

7. Judd, J. C, M. P. Wardell, and C F. Davidson. Extraction of 
Gallium and Germanium From Domestic Resources. Paper in Light 
Metals 1988. Metall. Soc. AIME, 1987, pp. 857-862. 



8. Neylan, D. L., C. P. Walters, and B. W. Haynes. Gallium 
Extraction From Phosphorus Flue Dust by a Sodium Carbonate Fusion- 
Water Leach Process. Paper in Recycle and Recovery of Secondary 
Metals. Metall. Soc. ATME, 1986, pp. 727-733. 

9. Federal Register. V. 41, No. 172, Sept. 2, 1976, pp. 37114-37115. 

OTHER SOURCES 



U.S. Bureau of Mines publications: 
Gallium. Ch. in Mineral Commodity Summaries, annual. 
Gallium. Ch. in Minerals Yearbook, annual. 
Gallium. Ch. in Mineral Facts and Problems, quinquennial. 



U.S. GOVERNMENT PRINTING OFFICE 611-012/00.024 

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